U.S. patent application number 09/904926 was filed with the patent office on 2002-12-12 for retrievable stent and method of use thereof.
This patent application is currently assigned to American Medical Systems. Invention is credited to Bolea, Stephen L., Hauschild, Sidney F., Neisz, Johann J., Polyak, Mark, Rykhus, Jr., Robert L., Staehle, Bradford G..
Application Number | 20020188344 09/904926 |
Document ID | / |
Family ID | 26968939 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020188344 |
Kind Code |
A1 |
Bolea, Stephen L. ; et
al. |
December 12, 2002 |
Retrievable stent and method of use thereof
Abstract
A removable stent system and method for extraction of a
removable stent from a target site is disclosed. The removable
stent includes-a removable stent having a collapsible end and a
collapsing element configured for coupling with a removal tool. The
collapsing element can be configured as a lasso or can be movable
between two positions when deployed at a target site in vivo. The
removable stent overcomes disadvantages and limitations of previous
types of stents as well as overcoming complications during or
following stent deployment in vivo. The removable stent further
includes features that increase its ease of use and reduce the
maneuvering required of devices or tools used to remove the stent.
This then decreases the amount of effort required by the physician,
the procedure time, and the level of discomfort experienced by a
patient during the procedure.
Inventors: |
Bolea, Stephen L.;
(Watertown, MN) ; Rykhus, Jr., Robert L.; (Edina,
MN) ; Hauschild, Sidney F.; (Brooklyn Park, MN)
; Neisz, Johann J.; (Coon Rapids, MN) ; Polyak,
Mark; (Minnetonka, MN) ; Staehle, Bradford G.;
(Minnetonka, MN) |
Correspondence
Address: |
Attension: Jeffrey J. Hohenshell
American Medical Systems
10700 Bren Road West
Minnetonka
MN
55343
US
|
Assignee: |
American Medical Systems
|
Family ID: |
26968939 |
Appl. No.: |
09/904926 |
Filed: |
July 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60295128 |
Jun 1, 2001 |
|
|
|
Current U.S.
Class: |
623/1.11 ;
623/1.15 |
Current CPC
Class: |
A61F 2/90 20130101; A61F
2/848 20130101; A61F 2002/9511 20130101; A61F 2002/9528 20130101;
A61F 2/95 20130101 |
Class at
Publication: |
623/1.11 ;
623/1.15 |
International
Class: |
A61F 002/06 |
Claims
what is claimed is:
1. A removable stent comprising a stent and a lasso: the stent
having an inner lumen, an outer surface and two opened ends,
wherein at least one opened end is collapsible; and the lasso
positioned toward the end of the stent that is collapsible, wherein
a portion of the lasso is engageable with a removal tool within the
inner and/or outer lumen of the stent.
2. The removable stent of claim 1, further comprising a lasso
having a loop disposed within the inner lumen of the removable
stent.
3. A removable stent, comprising: a stent having an inner lumen, an
outer surface, and two opened ends, wherein at least one opened end
is collapsible; and a collapsing element having first and second
ends, the first end coupled to the stent and the second end being
free, wherein at least a portion of the collapsing element between
its first and second end is coupled to the outer surface of the
stent, and the second end is substantially within the inner lumen
of the stent.
4. The removable stent of claim 3 further comprising a ball coupled
to the second end of the collapsing element.
5. A removable stent comprising: a stent having an inner lumen, an
outer surface, and two opened ends, wherein at least one opened end
is collapsible; and a collapsing element located on said stent,
said collapsing element being movable between a first and a second
position, wherein the collapsing element is in a down position when
in the first position.
6. The removable stent of claim 5 wherein the collapsing element is
a hinged hook.
7. A stent removal system comprising: a removable stent having an
inner lumen, an outer surface, two opened ends, wherein at least
one opened end is collapsible; a lasso positioned toward the end of
the stent that is collapsible, wherein a portion of the lasso is
disposed within the inner and/or outer lumen and includes an
engagement coupling for receiving a removal tool; and a removal
tool having at least one end configured for engaging with said
engagement coupling.
8. The system of claim 7 wherein said engagement coupling comprises
at least one of a loop, a ball, and a hook
9. A stent removal system comprising: a stent having an inner
lumen, an outer surface, and two opened ends, wherein at least one
opened end is collapsible; a collapsing element having a first end
and a second end, the first end coupled to the stent and the second
end being free, wherein a portion of the collapsing element between
the first and second end is in contact with the outer surface of
the stent and the second end is within the inner lumen of the
stent; and a removal tool having at least one end configured to
engage said free end of the collapsing element.
10. The system of claim 9 wherein the collapsing element comprises
a wire having a first end and a second end, wherein the first end
is coupled to the outer surface of the removable stent and the
second end is at least one of a ball, a loop and a hook disposed
within the inner lumen of the stent.
11. A stent removal system comprising: a stent having an inner
lumen, an outer surface, and two opened ends, wherein at least one
opened end is collapsible; a collapsing element movable between a
first and a second position, wherein the collapsing element is
normally placed in the first position when deployed in a target
site in vivo; and a removal tool having a first and a second end,
wherein the first end is configured to engage the collapsing
element.
12. The system of claim 11, further comprising a grasper element
configured for attachment to the removal tool.
13. The system of claim 12 wherein the grasper element is
configured for attachment to a stent delivery tool.
14. A removable stent comprising: a stent having an inner surfact,
an outer surface, and two open ends, wherein at least one open end
is collapsible and includes at least one loop disposed towards said
open end; and a collapsing element supported by said at least one
loop.
15. The removable stent of claim 14 wherein portions of said
collapsing element extend between at least two loops, said portions
begin accessible for engagement with a removal tool.
16. The removable stent of claim 14 wherein said collapsing element
contains flexures enabling a folded profile during constriction of
said open end of said stent.
17. A removable stent comprising: a stent having an inner lumen, an
outer surface, and two open ends, wherein at least one open end is
collapsible; and a collapsing element clipped onto said external
surface of said stent.
18. The removable stent of claim 17 wherein said collapsing element
is c-shaped.
19. The removable stent of claim 17 wherein said collapsing element
is spiral shaped.
20. The removable stent of claim 17 wherein ends of said collapsing
element are accessible for engagement with a removal tool
maneuvered between said external surface of said stent and a lumen
of a patient.
21. A method of removing a stent from a target site comprising:
providing a removable stent having an inner lumen, an outer
surface, a collapsible end and a collapsing element, wherein at
least a portion of said collapsing element contacts said outer
surface of said removable stent; maneuvering a tool toward said
removable stent such that said tool engages said collapsing
element; compressing said collapsible open end of said removable
stent through continued engagement of said collapsing element; and;
removing said removable stent from said target site.
22. The method of claim 21 wherein said tool is maneuvered within
said inner lumen of said removable stent.
23. The method of claim 22 wherein said collapsing element
comprises a lasso having a loop disposed within said inner lumen of
said removable stent.
24. The method of claim 23 wherein said collapsing element
comprises a wire having a first end and a second end; said first
end coupled to said stent and said second end being free, wherein a
portion of said wire between the first end and said second end is
in contact with said outer surface of said stent and said second
end is within said inner lumen of said stent.
25. The method of claim 24 wherein said second end of said wire
comprises at least one selected from the group consisting of a
ball, a loop, and a hook
26. The method of claim 21 wherein said collapsing element is
movable between an up and a down position when deployed in said
target site in vivo.
27. The method of claim 26 wherein said collapsing element is a
hinged hook.
28. The method of claim 21 wherein said tool is maneuvered toward
said collapsible end of said stent and said collapsing element
comprises a closed-loop structure woven through and acessible at
said collapsible end.
29. The method of claim 21 wherein said tool is maneuvered between
said outer surface of said stent and a lumen at said target site.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to a removable stent
and an assembly for its delivery or removal from a target site. The
present invention particularly relates to a removable stent and
system for its use in a medical procedure involving blood vessels,
ducts, treatment of enlarged prostate gland, coronary artery
disease and the like.
BACKGROUND OF THE INVENTION
[0002] Stents are used in a wide variety of medical procedures
where the permanent expansion of an occluded vessel is desired.
Usually, stents are constructed of a metal cylinder that is
implanted into a patient at the site of obstruction. In a patient
suffering from an occluded vessel, balloon catheterization or
balloon angioplasty is often the prescribed treatment. However,
following such a procedure, restenosis or re-narrowing of the
occluded tissue often occurs. Therefore, stents were developed and
are used to optimize and improve the initial and long-term outcome
in patients treated for an obstructed vessel. In addition to
obstructions, stents are also used to provide support for a graft
during healing of reconnected vessels. Diseases most often treated
using a stent include coronary artery disease, benign prostatic
hyperplasia (also referred to as an enlarged prostate gland), and
other medical indications where expansion of a lumen, vessel or
duct is desired. As such, a variety of stent systems have been
developed for medical use. See, for example, U.S. Pat. No.
5,100,429; U.S. Pat. No.4,762,128; and U.S. Pat. No. 4,800,882.
[0003] Although the development of stents for use in medical
procedures has been a major advance in treating a narrowed lumen, a
variety of complications can and do occur in connection with either
the delivery of the stent or, at a later time, following deployment
of the stent in vivo. Such problems or complications include
failure of proper deployment of the stent, misalignment,
dislodgement, or damage of the stent after it is deployed, or
re-occlusion of the vessel over time once the stent is inserted. In
these cases, removal of the stent is desired. Devices and/or
assemblies allowing for the extraction of a stent are known and
include, for example, U.S. Pat. No. 5,474,563; U.S. Pat. No.
5,624,450 and U.S. Pat. No. 5,411,507. In particular, Hendrik, U.S.
Pat. No. 5,624,450 describes an assembly for the removal of an
implanted stent. The assembly entails use of an expandable element
having an adhesive outer surface. The expandable element is
connected to a pulling device. Insertion followed by expansion of
the expandable element inside the faulty stent causes its
attachment (adhesion) to the inner surface of the stent allowing
the user to then "pull" the stent out. A particular disadvantage in
this system is that it is unreliable, as attachment of the
expandable element to the stent occurs by adhesion. As a result, a
more reliable and effective removal system is desired.
[0004] An example of an additional stent removal system may also be
found in U.S. Pat. No. 5,474,563, which describes a system for
removal of a cardiovascular stent device from a blood vessel. The
system includes a self-expanding elastomeric stent and an
extraction catheter for removal of the cardiovascular stent. The
extraction catheter is especially designed so as to specifically
engage with projections located on the stent. Removal of the stent
occurs by engaging the extraction catheter with the projections.
One disadvantage of this extraction system and other similar
systems is the requirement for complex extraction instrumentation
as well as specific and intricate maneuvering by the physician to
engage the extraction tool with the stent.
[0005] The above-described removal systems (and other similar
devices not specifically described) offer advantages, including
effectiveness and safety to both the user and the patient. However,
it has been discovered that an obstacle or disadvantage to such
devices is that their use is complicated. Additionally, even with
the more simple removal systems, the susceptibility of separation
of the removal device from the stent during use result in major
limitations to the reliability of these systems.
[0006] In view of the above, it is apparent that there is a need to
provide a removable stent and a system which allows for reliable
and minimally traumatic removal of a stent from an in vivo target
site. There is also a need to provide a removable stent and system
that is efficient, simpler to use for the physician and easy to
maneuver in vivo. A reliable and efficient removal system would
reduce the overall procedure time required, reduce possible trauma
to the lumen wall during use, and therefore reduce patient
discomfort during recovery. Such removal systems include properties
that reduce the amount of effort required by the physician prior to
and during use of the system as well as properties that ensure the
system remain intact during removal of the stent.
OBJECTS AND SUMMARY OF THE INVENTION
[0007] In view of the foregoing, it is an object of the present
invention to provide a removable stent device that addresses the
limitations and disadvantages associated with prior removal
devices, yet meets the needs of the users.
[0008] A further object of the invention is to provide a removable
stent system that is efficient, requires minimal effort by the user
and that is reliable.
[0009] Still another object of the invention is to provide a
removable stent assembly having a collapsing element configured
around the circumference of the stent so as to allow retrieval of
the stent by collapsing one end of the stent to a smaller
diameter.
[0010] A further object of the invention is to provide a stent
removal system where removal of the stent can be achieved by use of
a simple removal tool having a grasper attachment. In one aspect of
the invention, a stent removal system for removing a stent from a
target site in a patient is disclosed. The system can include a
removable stent that is collapsible at a proximal end by engagement
of a collapsing element with a removal tool. The collapsing element
can be a lasso or a discontinuous lasso configured so as to
collapse the proximal end of the removable stent for removal from a
body site. Alternatively, the collapsing element can be a hook that
is movable between an up and a down position. The removal tool is
configured so as to allow coupling to the collapsing element of the
removable stent. The removal tool can be configured as a tube
having a slot at one end allowing for its coupling to the
collapsing element. The stent removal system can also include a
grasper element designed to aid in the removal of the stent by
attachment to a removal tool or a delivery tool.
[0011] An additional object of the invention is to provide a method
of removing a stent in vivo using a stent removal system.
[0012] These and other objects not specifically enumerated herein
are believed to be addressed by the present invention which
contemplates a stent removal system for removing a stent from a
body site that includes a removable stent having a collapsible
proximal end, a collapsing element and a removal tool.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a side view of a preferred embodiment of the
present invention in sztu including a removable stent having a
collapsible proximal end, an inner lumen and a collapsing
element;
[0014] FIGS. 2A and 2B are enlarged views of the area of a
removable stent having a hinged hook collapsing element depicting
the hinged hook in upright (FIG. 2A) and down (FIG. 2B)
positions;
[0015] FIG. 3 is a cross-sectional view of a removable stent along
the 3-3 line of FIG. 1;
[0016] FIGS. 4A and 4B are cross-sectional views through the hinge
region of a hook type of collapsing element;
[0017] FIG. 5 is a side view of a removable stent including a
removal tool for grasping a collapsing element of a removable
stent;
[0018] FIG. 6 is a cross-sectional view of a removable stent along
line 6-6 of FIG. 5;
[0019] FIG. 7 is a side view of a removable stent in situ with the
proximal end in the collapsed position;
[0020] FIG. 8 is a view of a removable stent having a lasso
collapsing element;
[0021] FIG. 9 is a cross sectional view through the proximal end of
a removable stent having a lasso collapsing element;
[0022] FIG. 10 is a view of a removal tool and a removable stent
having a lasso collapsing element;
[0023] FIG. 11 is a view of a removal tool grasping a removable
stent;
[0024] FIG. 12 is a view of a removable stent having a
discontinuous lasso collapsing element;
[0025] FIG. 13 is a cross sectional view through the proximal end
of a removable stent having a discontinuous lasso collapsing
element;
[0026] FIG. 14 is a view of a removal tool grasping a removable
stent;
[0027] FIG. 15 a view of a removal tool grasping a removable
stent;
[0028] FIG. 16 is an enlarged view of an area of an alternate
embodiment of a removable stent having eyelets or loops formed near
the end of the stent;
[0029] FIG. 17 is a detailed view of an alternate embodiment of the
loop of FIG. 16;
[0030] FIG. 18 is an enlarged view of an area of an alternate
embodiment of the removable stent of FIG. 16;
[0031] FIG. 19 is a partial view of the removable stent of FIG. 16
having a lasso-type collapsing element;
[0032] FIG. 20 is a partial side view of a removal tool and the
removable stent of FIG. 17;
[0033] FIG. 21 is a side view of the removable stent of FIG. 17 in
a constricted configuration;
[0034] FIG. 22 is a side view of a removable stent and an alternate
embodiment of a collapsing element;
[0035] FIG. 23 is a side view of a removable stent and an alternate
embodiment of a collapsing element; and
[0036] FIG. 24 is a view of a grasper device for attachment to a
removal or a delivery tool.
DETAILED DESCRIPTION OF THE INVENTION
[0037] FIG. 1 shows a representative view of a removable stent 10
in situ within a body vessel 11. For convenience and ease of
comprehension, the medical device referenced in the text and
figures of the present disclosure is a stent. However, it should be
noted that other medical devices or prosthesis including, but not
limited to, balloons, stent coverings, vascular grafts, or other
implantable devices, are also within the scope of the claimed
invention.
[0038] The removable stent 10 is an intraluminal prosthesis or
device having proximal 22 and distal ends 24 that are open. The
removable stent is generally tubular in shape and has an outer
surface 30 which contains an inner lumen 32 that extends axially
between collapsible proximal 22 and distal ends 24. A removable
stent includes collapsing elements 40, which aid in collapsing or
compressing the stent 10 for its removal from an intralumenal site.
The collapsing element 40 of the stent is a feature that aids in
its efficient and easy removal from a body lumen. As used herein,
the term "proximal" is intended to refer to the end of the stent
closest to the physician when deployed at a target site, or the end
that will be collapsed for removal of the deployed stent from its
target site. The "distal" end is intended to refer to that end
which is opposite to the proximal end 22.
[0039] A removable stent 10 can be of the type that is self
expanding, or of the type that is expandable using a balloon
mechanism. Methods for the construction, manufacture or deployment
of self-expanding stents are known in the art and are described,
for example, in U.S. Pat. No. 5,356,423 aswell as in U.S. Pat. No.
4,655,772. Balloon expandable stents are also known in the art and
are described, for example, in U.S. Pat. No. 4,893,623.
Alternatively, the stent can be expandable by any other means, or
can be of any variety of expandable prostheses or intralumenal
implantation devices that include an element capable of collapsing
or constricting the stent from an end, such as the proximal
end.
[0040] Referring to FIG. 1, a removable stent 10 can be constructed
so as to have a mesh structure 26. The mesh can be made of elongate
elements, such as metal wires, that are woven, braided, or stamped.
Alternatively, the mesh-work can be formed from any other type of
material or structure so long as it is biocompatible and of
sufficient rigidity so as to support patency of a body lumen or
target site when implanted in vivo. Biocompatible materials
suitable for such construction include, for example, stainless
steel, alloys, composite materials, or plastics. The removable
stent can also be constructed of a flexible or non-metallic
material such as an elastic polymer or rubber, medical-grade nylon
or polyester, or any material that is either itself collapsible or
can be formed or configured to be compressible.
[0041] In a preferred embodiment, as shown in FIGS. 1 and 7, the
removable stent 10 is a braided tubular mesh 26, constructed of a
collection of wires 28 (approximately 24 in number) held together
by friction. The wires are formed or woven in such a way so as to
facilitate and maintain radial expansion of the stent when deployed
in vivo (See FIG. 1), while also allowing for radial compression of
the stent when pulled along its longitudinal axis (FIG. 7). The
expansion/compression feature of the removable stent 10 is designed
such that application of a pulling force along the stent's
longitudinal (x-x) axis results in radial compression and reduced
lumen diameter. Release of the longitudinal force returns the stent
to its deployed radially expanded dimension. This feature of the
removable stent is similar to the mechanism employed in a child's
Chinese handcuff toy.
[0042] A collapsing element 40 can be of a variety of structural
configurations. The collapsing element 40 is preferably located at
or near the proximal end 22 of the removable stent 10 as this is
generally the end from which the physician will first encounter the
stent during a removal procedure. In a preferred embodiment, a
removable stent can include a collapsing element 40 designed as a
clasping structure that is located within the inner lumen 32 of the
removable stent as shown in FIG. 1 and 3. FIG. 3 is a
cross-sectional view of a removable stent taken along the 3-3 line
at the proximal end 22 of the removable stent 10 of FIG. 1. Such a
collapsing element 40 (also referred to herein as a "hinged hook"
or a "hook"e) is movable between a first and a second position.
Therefore, as illustrated in FIG. 2 the hook elements 42 can be
lifted into an upright or "up" position (FIG. 2A) for engagement
with and extraction by a removal tool, or can be pushed into a
"down" position (PIG. 2B) where it lays flat against the inner wire
surface 42 of the removable stent when the stent is deployed in
vivo. As illustrated in FIG. 3, when in the "up" position, the
hooks 40 protrude away from the inner surface 30 of the stent into
the inner lumen 32. A removable stent having a hinged hook type of
collapsing element 40 will preferably include 2 to 3, or 3 to 4
hooks, spaced equally along the inner circumference or surface 30
of the removable stent.
[0043] FIGS. 2A and 2B are enlarged views illustrating a hook type
of collapsing element 40 of a removable stent when deployed in
vivo. When in the first or "down" position (FIG. 2B), the hook
element 40 resides substantially parallel to or flat against the
inner surface of a cross wire 42 of a stent. The ability of the
hook 40 to lay flat against the inner surface of the removable
stent ("down" position) is particularly advantageous in that such a
collapsing element 40 will not interfere with the patency, impede
the flow, or increase the possibility of clot formation of a fluid
through the stent. This is of particular concern when a stent is
deployed in a blood vessel. A collapsing element 40 that is movable
between an up and a down position allows for placement of the
collapsing element 40 into a more accessible position for
engagement with a removal tool. This aspect of the present
invention provides a more versatile and effective removable
stent.
[0044] A hinged hook type of collapsing element 40 includes an
upper region that is curved or shaped as a hook 44. The lower or
bottom portion 46 of the collapsing element 40 is configured so as
to enclose or wrap around a wire 43 of the stent so as to function
as a -hinge. The collapsing element 40 can be attached to a stent
wire 43 at the inner surface of the removable stent. A hinged hook
44 can be designed or configured so as to snap onto a stent wire 43
with a portion 46 of the hinged hook disposed toward the outer
surface of the stent. Once snapped into place, the hinged hook 44
can be pushed or slid along the stent wire 43, passing underneath a
crossing wire 41, so as to position the hook 44 underneath a cross
wire 42 as shown in FIG. 2B.
[0045] In addition, a hook type of collapsing element can be
configured so as to include tab components, which allow it to be
easily snapped or clipped onto a stent wire. Referring to FIGS. 4A
and 4B detailed cross-sectional views through the hinge portion 46
of a hook 44 illustrate two exemplary designs of tab components of
a hook hinge region. In the first design (FIG. 4A), the tab gap
element 8 is an extension of the hinge portion 46 that, when
pressed, will become captured in the hinge latch 47 which is an
extension of the hook 44. In the second design (FIG. 4B), the hinge
latch 47 is pressed such that it becomes captured by the tab gap
element 8. Both of these hinge designs allow rotational movement of
the cross wire 43 relative to the hook 44. That is, the hinge 46
portion of a hook type 44 of collapsing element 40 allows the
collapsing element to be movable between its deployed, "down"
position and a removable "up" position. A hinged hook 44 type of
collapsing element as described herein is also advantageous in that
the tab gap design reduces undesired movement of the hook element
44 between its two positions (upright or down) by virtue of how the
tab gap design is comprised around and in frictional contact with
the cross wire 43. Therefore, a hinged hook is preferably
manufactured of a material that maintains a certain degree of
resistance so as to ensure the collapsing element remains in either
the up or the down position, as is desired by the physician during
use. A hinge material can be manufactured of a same material as the
stent wire, such as stainless steel or plastic. An optimal method
of fabricating and handling a hinged hook is by continuous metal
stamping on a band or a ribbon.
[0046] A stent of the present invention can be removed from an
intralumenal site by collapsing one of its ends, such as the
proximal end, with the aid of a removal tool. Several types of
removal tools 62 can be used to remove a stent 10 of the present
invention, as will be apparent to one skilled in the art. Referring
to FIG. 5, a removal tool 62 suitable for use with a hook type of
collapsing element 40 can be designed to have coupling structure 64
for engaging the hook elements 40. The stent 10 can then be
collapsed beginning at its proximal end 22 using the removal tool
62 to grasp the hooks 40 and to apply a pulling force. FIG. 6
illustrates a cross-sectional view of a removable stent having hook
elements 40 engaged with a removal tool. As indicated in FIG. 6,
application of a rotational force on the constricting elements 40
via the coupling means 64 collapses the stent 10 radially
inward.
[0047] In a preferred embodiment, a removal tool 62 can take the
form of a standard stone basket tool. One such tool includes a
stone basket as manufactured by Cook Urologic. In this embodiment,
the strands forming the basket of the tool engage the hooks 40 as
shown in FIG. 6.
[0048] FIG. 7 illustrates a stent 10 of the present invention
during removal from an intralumenal site 11. Radial constriction
begins at the proximal end 22 of the stent 10 extending toward the
distal end 24 longitudinally, as the stent 10 is pulled by a
removal tool 62 coupled to the collapsing elements 40. Radial
compression and collapse of the stent 10 beginning with the
proximal end 22 allows the physician to easily withdraw or ensnare
the stent 10 into an endoscope sheath for its removal from an in
vivo intralumenal site 11. This aspect of the removable stent 10 is
particularly advantageous to achieving the goals of the invention
in that a stent 10 having a collapsible end allows for easy
manipulation of the stent 10 into a catheter or endoscope sheath to
completely remove the stent 10 from the patient's body.
[0049] Referring to FIG. 8, a collapsing element can also be
configured as a lasso 80 situated around the circumference of the
proximal end 22 of a stent 10. The lasso 80 is constructed of a
wire which functions as a noose capable of constricting or
tightening itself around the outside surface 82 of the stent 10.
The lasso 80 can include a loop region 84, which allows for
engagement of a removal tool 101 to grasp and remove the stent 10
(see FIG. 10). The loop region 84 of the lasso 80 is disposed
internally within the stent 10 with the remainder of the lasso wire
86 wrapped externally around the stent 10. Alternatively, the lasso
80 can be woven into and out of the stent surface 82. Therefore,
the lasso 80 is preferably incorporated substantially around the
circumference on the outside surface 30 of the stent 10.
[0050] As illustrated again in FIG. 9, the inner lumen 90 of the
removable stent 10 has a cross-sectional diameter, along its x-x,
or its y-y axis, which dimensions can vary depending on use. FIG. 9
shows a cross-sectional view of a removable stent 10 when expanded.
The diameter of the inner lumen 90 can vary between a relatively
larger diameter such as when the stent is deployed, and a
significantly smaller diameter. Therefore, when the proximal end 22
of the stent is collapsed, through constriction of the lasso 80,
the inner lumen will have a reduced cross-sectional diameter
allowing for its extraction from an intralumenal site (see FIG.
11). This aids the physician in removing the stent from its target
site with minimal damage or trauma to the surrounding tissue.
[0051] FIGS. 10 & 11 shows views from internal perspectives
(inside viewing outward) of a removable stent 10 during collapse
and removal of the stent 10. The lasso 80 type of collapsing
element functions by radial contraction, which collapses a
removable stent 10 from an expanded diameter (FIG. 10) to a reduced
diameter (FIG. 1 1). The loop region 84 of the lasso 86 protrudes
into the inner lumen of the removable stent 10, thereby allowing
the physician to grasp the lasso 84 by a hook element 102 disposed
at the end of the removal tool 101 (FIG. 10). Constriction of the
proximal end 22 of the stent 10 is achieved by rotating the removal
tool 101, which causes the lasso to twist upon itself, thus also
collapsing the stent 10. Alternatively, the lasso can be designed
to include internal elements such as a ball, a hook, or a loop that
assists in locating as well as operating the lasso. The lasso 80,
therefore, constricts or collapses the proximal end 22 of the
removable stent 10 by radial tightening 88 of the lasso 86 upon
itself. A lasso type of collapsing element can be constructed from
permanent materials (stainless steel, or metal wire, for example)
or from temporary degradable materials.
[0052] Referring to FIGS. 12-15, in a further embodiment of the
present invention, the collapsing element of a removable stent 10
need not extend over the entire circumference of the removable
stent 10 as a lasso or a noose, but can be a collapsing element
that is a discontinuous type of lasso. Referring to FIG. 12, the
collapsing element includes a discontinuous lasso 120 having a
first end 122 and a second end 124. The first end 122 is attached
or anchored to the proximal end 22 of the removable stent 10. This
attachment can be permanent if desired. The second end 124 of the
collapsing element or discontinuous lasso 120 is not attached to
the stent, but is freely associated with the stent 10. This allows
for the free expansion of the stent as needed in vivo. At least a
portion of the discontinuous lasso between its first and second
ends is juxtaposed, adjacent or interwoven to the outer surface 30
of the stent 10.
[0053] A discontinuous lasso 120 can be a wire 128 that is woveri
in between the wires 26, 28 forming the removable stent 10. The
discontinuous lasso 120 is connected to the removable stent 10 at a
diamond 140 that is formed by the weaving of the wires 142
comprising the removable stent 10. The second end 124 of the
discontinuous lasso 120 includes a ball 126 which protrudes into
the lumen 32 of the stent 10, thereby allowing the user access to
the discontinuous lasso 120 by insertion of a removal tool 150 into
the lumen of the stent 10. The diameter of the ball 124 is slightly
larger than the diagonal diameter of the diamond 140, thereby
maintaining the ball 126 within the inner lumen 32 of the stent 10.
When the removable stent 10 is expanded, the ball 126 is seated
partly within a diamond 140. The removable stent 10 can, therefore,
freely expand to any given cross-sectional diameter without being
restricted by its collapsing element. The design of a discontinuous
lasso type of constricting element allows for a freely associated
second end 124 which does not restrict expansion of the removable
stent 10.
[0054] Referring to FIG. 14 & 15, in order to collapse and
remove a stent having a discontinuous lasso type of collapsing
element 120, a removal tool 150 is used. An example of such a tool
is shown in FIG. 14. The removal tool 150 can be configured as a
cylindrically shaped tube having a slot 152 disposed at its end.
The removal tool should be sufficiently rigid so as to allow the
user to easily maneuver and engage the ball 126 of the collapsing
element 122 into the slot 152. The slot 152 is slid underneath the
ball 126 of the collapsing element 120 (FIG. 14), thereby lifting
the ball 126 out of its seating within the stent 10. Once the ball
126 is lifted, the removal tool 150 is twisted, wrapping the wire
of the discontinuous lasso 128 around the outer surface of the
removal tool 150. Because the pulling force of the discontinuous
lasso 120 and the holding force of the removable stent 10 are at
the tip 154 of the removal tool 150 (FIG. 14) the proximal end 22
of the stent 10 is easily collapsed (FIG. 15), enabling the
physician to pull or withdraw the collapsed stent away from the
implanted site in vivo.
[0055] In another embodiment of the invention, shown in FIGS. 16 to
21, the removable stent 10 includes one or more eyelets or loops
170 formed at or near the ends of the elongate elements or wires
172 of the stent 10. The loops 170 can be shaped either before or
after the wires 172 are assembled into the mesh-structure that
forms the stent 10. The shape of the loops 170 can include
"p"-shaped, helical, twisted, oval, circular, diamond, square or
any other similar configuration that forms a hole capable of
receiving and/or capturing a cord-like member, such as a lasso 80.
The design and alignment of the loops 170 at the ends of the wire
elements 172 are configured to prevent the loops 170 and/or lasso
80 from projecting or extending into the interior of the stent 10.
This, in turn, reduces the potential for encrustation or clot
formation within the lumen of the implanted stent 10.
[0056] In one embodiment, at least one end of the wire element 172
is twisted or wound into a loop 170. Although the material
characteristics of the wire element 172 maintain the end of the
wire element 172 in a loop configuration, a resistance laser weld,
crimp or other connection can be made at the location on the loop
170 where the wire element 172 crosses over itself. The resistance
weld can be used to further secure the end of the wire element 172
in a permanent loop arrangement.
[0057] In an alternate embodiment, the elongate element 172 can be
laser-cut, stamped or punched from a sheet of material. As shown in
FIG. 17, at least one loop 170 is formed at an end of the stamped
element 172. Other embodiments of forming the loop 170, though not
specifically described herein, are also included within the scope
of the claimed invention.
[0058] Referring to FIG. 16, the mesh-structure of the stent 10 is
formed from two sets or groups of parallel wires 172. The first set
of parallel wires 174 is placed at approximately a 90 degree angle
with respect to the second set of parallel wires 176, forming a
diamond-shaped pattern 178 of wire elements 172. However, the
actual placement of the two sets of parallel wires 174, 176 may
vary within the range of 10 degrees to 170 degrees. As shown in
FIG. 16, a loop 170 is formed at or near an end of every other wire
172 of the first set of parallel wires 174. The configuration of
the first set of wires 174, in particular the placement of the
wires 172 so that each wire end rests on the external surface of a
wire element 172 (whereby the external surface of the wire element
172 corresponds to the outside surface 82 of the stent 10, not
shown) from the second set of wires 176, further enhances the
constriction characteristics of the stent 10. In addition, this
configuration also prevents potential flaring of the distal end of
the stent 10 as the proximal end 22 of the stent 10 is constricted
or collapsed during stent removal. Flaring of the distal end of the
stent 10 not only impedes stent removal, but also causes the wire
ends to anchor or embed into the wall tissue of the lumen. Thus,
the loop design at the ends of the wire elements 172 also mitigates
potential tissue trauma associated with the stent removal
procedure.
[0059] In another embodiment of the invention, shown in FIG. 18, a
total of at least three loops 170 are formed at the ends of the
wires 172 near the proximal end 22 the stent 10. In general, the
loops 170 are formed at the ends of the wires 172 and a lasso-type
element is woven through the loops 170. Placement of the loops 170
at the ends of the wires 172 improves user accessibility to the
lasso for facilitated stent 10 removal. In another embodiment, the
loops 170 can be formed anywhere within the region approximately
two diamonds 178 distal to or 10 mm or 5 mm (0.39 inches or 0.020
inches) from the ends of the wire elements 172.
[0060] As shown in FIGS. 19 and 20, the lasso 80 type collapsing
element is woven or threaded through the loops 170 of the stent 10.
In one embodiment, the lasso 80 type collapsing element is a
flexible closed-loop or ring-like structure. When the stent 10 is
in an expanded configuration, portions of the lasso 80 extending
between each loop 170 are easily accessible for engagement from the
end of the stent 10 in vivo using a standard alligator gripper or
custom removal tool 178. As such, the stent 10 is removed from the
lumen of the patient by twisting the removal tool 178 so that the
lasso 80 wraps around the outer surface of the removal tool 178 or
pulling the lasso axially. Because the pulling force of the lasso
80 and the holding force of the removable stent 10 are at the tip
of the removal tool 178, the proximal end 22 of the stent 10 is
easily collapsed, enabling the physician to pull or withdraw the
collapsed stent 10 away from the implanted site in vivo. Referring
to FIG. 21, during constriction of the proximal end 22 of the stent
10, the lasso 80 is configured so that it acquires a folded
profile. The folded configuration of the lasso 80 prevents portions
of the lasso 80 from hanging into the lumen and causing associated
blockages or clot formations. As such, any slack or folds in the
lasso 80 is generally held or captured between the external surface
of the stent 10 and the tissue wall of the patient's lumen.
[0061] In an alternate embodiment, the collapsing element of the
removable stent 10 need not extend over the entire circumference of
the removable stent 10 as a lasso or a noose does. As shown in
FIGS. 22 and 23, the collapsing element can be a discontinuous
spiral 180 or c-shaped 182 clip member. In general, the spiral 180
or c-shaped 182 clip member can be fabricated from a rigid or
semi-rigid material. As with the elongate elements 172 of the stent
10, the clip member 180, 182 can be fabricated from a variety of
materials including, but not limited to, laser cut, woven, braided,
or stamped. Various other material types and configurations may
also be used provided that the type of material or structure is
biocompatible and of sufficient rigidity so as to support
constriction of the stent 10. Examples of suitable biocompatible
materials include, but are not limited to, stainless steel, alloys,
composite materials, plastics, or other non-metallic materials such
as an elastic polymer or rubber, medical-grade nylon or
polyester.
[0062] In one embodiment, the spiral or c-shaped member 180, 182 is
attached or clipped onto the external surface of the stent 10. To
constrict the stent 10, a removal tool is maneuvered between the
external surface of the stent 10 and the lumen of the patient and
engages/grasps the ends 184 of the clip member 180, 182. Using the
tool, the ends 184 of the clip member 180, 182 are then moved
toward each other and/or, depending on the desired degree of
constriction of the stent 10, past each other. Radial constriction
of the clip member 180, 182 causes inward collapse or radial
contraction the stent 10. In an alternate embodiment, one end of
the clip member 180, 182 is attached or secured to the stent 10
(not shown). As such, the removal tool need only grasp or engage
the unattached end of the clip member 180, 182, moving the free end
of the clip member 180, 182 toward and/or past the secured end. As
with the previous embodiment, constriction of the clip member
produces radial contraction of the stent 10, without causing the
stent 10 to rotate within the lumen of the patient.
[0063] Due to the dynamic nature of living tissue, ingrowth can
occur around an implanted stent. As a result, it is sometimes
necessary for the physician to resect or cut the implanted stent
away from the surrounding tissue. As such, heated methods of
resection are often used to cut the stent out. Therefore, a lasso
type collapsing element 120 can be a wire constructed of a material
that is resistant to heat during resection, such as a flexible
carbon fiber substance. In addition, the discontinuous lasso 120
can be coated with an anti-adhesive substance such as heparin, or
other pharmaceutical or chemical agent which aids in preventing
adherence of tissue to the collapsing element.
[0064] As disclosed above, a collapsing element can be configured
in a number of ways and is preferably designed so as to allow the
user to grasp the stent and collapse the proximal end of the stent.
It should be noted, however, that also included in the present
invention is a removable stent having a collapsing element whose
location is not at or restricted to the proximal end of the stent.
For example, a collapsing element can be disposed anywhere along
the length of the stent so long as the collapsing element is
designed so as to be capable of collapsing an end of the stent.
This allows for removal of the stent from an intraluminal site with
minimal damage to adjacent tissue or intraluminal wall of the
target site.
[0065] A variety of tools or devices can be used to grasp the
collapsing element of a removable stent. In addition to the removal
tool as described above, stone or basket extractors or grasping
forceps known in the art can be used with the present invention.
For example, with a removable stent having a hinged hook type of
collapsing element, a physician can use a basket extractor to
engage and grasp the hinged hooks. Using a stone extractor, for
example, the physician will first position the hooks into their
upright position (while viewing the deployed stent through a
cystoscope). Once upright, the physician then engages the wires of
the extractor with the hooks, thereby grasping the stent by the
collapsing elements. By collapsing the wires of the extractor, the
physician also pulls on the collapsing elements, thereby collapsing
the proximal end of the stent. Once collapsed, the stent can then
be pulled into the sheath of the cytoscope.
[0066] An additional aspect of the present invention comprises a
removal attachment or grasper for use with a delivery tool to
engage or grasp the removable stent. FIG. 24 shows a view of a
removal attachment 200 that can be used with a removal tool.
Alternatively, such an attachment can be attached or used with a
stent delivery tool. Removal tools suitable for use with a removal
attachment include those described herein as well as others known
in the art, such as the Urolume Delivery System. Stent delivery
tools suitable for use with a removal attachment include the
Urolume Delivery System.
[0067] The removal attachment includes a base portion 202 that is
tubular in shape. The base portion 200 has a front end 208 and a
back end 210. The base portion 202 includes an element 204 disposed
at the back end 210 which locks the removal attachment 200 to a
delivery tool such as a grapple. The front end 208 of the removal
attachment 200 includes prong(s) 212 that are configured or shaped
as curved finger-like projections that extend outward or away from
the removal attachment 200. The prong(s) 212 can be manipulated so
as to grasp or hook a collapsing element of a removable stent. One
aspect of the removal attachment that is particularly advantageous
to achieving the goals of the invention is that it is designed to
be adaptable with a wide variety of tools used in the art for
delivery and/or removal of a stent.
METHOD FOR EXTRACTION OF A REMOVABLE STENT
[0068] The methods and devices of the present invention provide
simple, accurate and stable removal of a stent or prosthesis from
an intraluminal or other, site in vivo. The features of the
invention, as described herein, provide a removable stent and
system that is reliable and less awkward or cumbersome for the
physician to use.
[0069] The present invention can be used for a variety of medical
treatments where removal of a stent from a patient is or may be
desirable. For example, in the treatment of an enlarged prostate
gland, a stent is often placed in the patient's urethra,
intraluminally at the site of compression by the enlarged prostate.
The deployed stent is often intended as a permanent means of
providing support and radial expansion to the constricted urethra
so that urine flow from the bladder through the compressed site is
remedied. However, failure of the implanted stent to function
properly can occur. For example, over time, tissue ingrowth from
the urethral wall through the openings of the stent wall can occur,
resulting in reobstruction or restenosis of the lumen. The present
invention is particularly advantageous in that it has elements
allowing for its easy access, and removal in vivo should the need
arise to remove or explant the stent after deployment. Therefore,
the present invention can function as a permanently implanted stent
or as a temporary or removable stent in vivo. Use of the present
invention in medical indications requiring stent treatment adds a
precautionary measure not provided in permanent stent implants or
prostheses.
[0070] Depending upon the location of the deployed stent and/or the
physician's preference, a removable stent can be extracted using a
removal tool and withdrawn into a catheter or a sheath of a viewing
instrument. For example, as shown in FIG. 10, with a removable
stent 10 having a lasso type of collapsing element 80, a removal
tool 101 having a hooked end 102 is first inserted into a patient's
urethra through a viewing instrument, up to the site of the
deployed stent. Once at the stent, the physician engages the hooked
end of the removal tool 101 with the loop 84 portion of the
collapsing element 80. The physician maneuvers by twisting or
rotating the removal tool so as to cause the lasso 80 to constrict
upon itself Tightening of the lasso 80 around the stent 10
collapses the proximal end 22 of the removable stent 10 (FIG. 11).
The collapsed end of the removable stent is then easily aimed into
the lumen of an extraction catheter or the sheath of a cystoscope.
Once inside the lumen, the stent 10 is extracted by further pulling
on the lasso 80, which is coupled to the stent. The remainder of
the stent 10 is then pulled away from and out of its in vivo
site.
[0071] Alternatively, as described previously, where a stent having
an alternative collapsing element configuration is to be removed,
there are a variety of commercially available devices that can be
used as the removal tool. If the deployed stent comprises a
swinging hook type of collapsing element, a removal tool such as a
loop snare, wire basket stone extractor, stone forceps, or other
device can also be used to grasp and withdraw the deployed stent.
These types of devices are known in the art, available
commercially, and described, for example, in U.S. Pat. No.
5,330,482. A basket retrieval device can be used to catch or engage
the stent from its internal lumen. As described previously, when
deployed in a target site, a removable stent can have a hinged hook
collapsing element in a down position so as not to impede the fluid
flow. In order to collapse the proximal end of the stent, the
physician can position the hook(s) into an upright or up position.
The resistive characteristics of the hinge portion of the hook
maintains the collapsing element in the up position, allowing the
physician to manipulate the wires of the basket retrieval device
until they engage with the hooks. Retraction of the basket pulls on
the collapsing element, which collapses the proximal end of the
stent. The stent is withdrawn and removed from the patient.
[0072] The systems and methods of the present invention provide
accurate, easy to use and stable grasping of a stent allowing for
its safe removal from a target site in vivo. The features of the
invention, as described herein, also provide a removable stent that
is less awkward or cumbersome for the physician to use.
[0073] Although the invention has been described in terms of
particular embodiments and applications, one of ordinary skill in
the art, in light of this teaching, can generate additional
embodiments and modifications without departing from the spirit of
or exceeding the scope of the claimed invention. Accordingly, it is
to be understood that the drawings and descriptions herein are
proffered by way of example to facilitate comprehension of the
invention and should not be construed to limit the scope
thereof.
[0074] All publications and patent applications in this
specification are herein incorporated by reference to the same
extent as if each individual publication or patent application was
specifically and individually indicated by reference.
* * * * *